Sports fans in the United Kingdom can't seem to get enough of unified heavyweight titleholder Anthony Joshua.

Joshua is scheduled to defend his world title belts against mandatory challenger Kubrat Pulev on Oct. 28 at Principality Stadium in Cardiff, Wales, and when tickets went on sale Monday fans snapped up approximately 70,000 on the first day, according to Matchroom Boxing promoter Eddie Hearn.

The fight became the fastest-selling event in Principality Stadium, which likely will hold close to 80,000 for the fight.

"It was another incredible day at the box office for Anthony Joshua as he continues to cement his place as the biggest draw in world boxing," Hearn said. "The support he receives from the British public is incredible and has been an integral part of his success. The fans will be in for a great night on Oct. 28 and we thank them all for their support."

Anthony Joshua, left, will make his fourth title defense when he takes on mandatory challenger Kubrat Pulev on Oct. 28. Nick Potts/AP

Joshua (19-0, 19 KOs), 27, of England, will be making his fourth title defense when he takes on Pulev (25-1, 13 KOs), 36, of Bulgaria. Joshua is coming off an epic slugfest against former longtime heavyweight world champion Wladimir Klitschko, whom he knocked out in the 11th round to retain his belt and win a vacant one before a British boxing record crowd of 90,000 at Wembley Stadium in London.

Klitschko retired after the fight rather than exercise his right to an immediate rematch, so Joshua instead will face Pulev, whose only loss was by fifth-round knockout to Klitschko in the 2014 knockout of the year.

The Joshua-Pulev card also will include junior bantamweight titlist Kal Yafai, of England, defending his belt against Japanese mandatory challenger Sho Ishida and Ireland's Katie Taylor challenging Anahi Esther Sanchez for a women's lightweight world title.